Bulb-operated pipet

ABSTRACT

A liquid transfer pipet consisting of a tubular barrel having an inlet conduit portion at one end and a reduced stem at the other end having a capillary bore. An apertured operating bulb is slidably and sealingly engaged on the stem. The capillary bore acts to allow filling of the barrel but substantially prevents liquid from entering the bulb because it allows the operator time to remove his finger from the vent aperture of the bulb. The capillary bore is of sufficiently small diameter to provide stable retention of liquid contained in the barrel. The operating bulb may form part of the cap or stopper of a bottle, vial, or similar vessel. The capillary bore may be formed merely in a solid top extension of the pipet main barrel without requiring the formation of a reduced stem.

May 6, 1975 United States Patent [191 Shapiro BULB-OPERATED PIPETPrimary ExaminerRichard E. Aegerter Assistant Examiner-Frederick R.Schmidt Attorney, Agent, or Firml-lerman L. Gordon [57] ABSTRACT Aliquid transfer pipet consisting of a tubular barrel [22] Filed:

[21] App]. No.: 430,384

having an inlet conduit portion at one end and a re- [52] US. Cl.141/24; 14l/29; 222/420 duced Stem at the other end having a capillarybore. [51] Int Cl B65b 3/04 An apertured operating bulb is slidably andsealingly engaged on the stem' The capillary bore acts to allow fillingof the barrel but substantially prevents liquid from entering the bulbbecause it allows the operator Field of search'IIIIIIIIIIIIIIII...

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time to remove his finger from the vent aperture of [56] ReferencesC'ted the bulb. The capillary bore is of sufficiently small di- UNITEDSTATES PATENTS ameter to provide stable retention of liquid contained inthe barrel. The operating bulb may form part of the cap or stopper of abottle, vial, or similar vessel. The

capillary bore may be formed merely in a solid top extension of thepipet main barrel without requiring the formation of a reduced stem.

XXXX 30016 32 2 45/ l 002 4 A an 2 2 6 Claims, 6 Drawing FiguresRATEN'TEDHAY 5 I975 FIE.5

PIES

FIG .4

BULB-OPERATED PIPET This invention relates to liquid transfer devices,and more particularly to a pipet of the bulb-operated type.

A main object of the invention is to provide a novel and improvedbulb-operated liquid transfer pipet which is very simple inconstruction, which is easy to operate, and which is volumetricallyprecise.

A further object of the invention is to provide an improvedbulb-operated pipet which is versatile in use, which is easy to control,and which acts to automatically substantially terminate liquid intakeaction as soon as its barrel is completely filled with liquid, theintake action being terminated by the resistance to flow of a capillarycolumn, the resistance to flow being sufficient to give the operatortime to discontinue the application of filling pressure.

A still further object of the invention is to provide an improvedbulb-operated liquid transfer pipet which is compossed of relativelyinexpensive and easily manufacturable parts, which extracts highlyaccurate measured volumes from liquid containers, and which allows saidmeasured volumes to be safely and reliably transferred without loss.

A still further object of the invention is to provide an improved liquidtransfer pipet of the bulb-operated type which is constructed so thatsubstantially all of its liquid retention chamber is visible to theoperator and so that he can quickly terminate filling pressure when thechamber is filled.

A still further object of the invention is to provide an improved liquidpipet, which once filled can be placed in any position or handled fairlyroughly without losing its contents.

A still further object of the invention is to provide an improved pipetclosure for containers of diagnostic test reagents.

A still further object of the invention is to provide an improvedbulb-operated liquid transfer pipet wherein the operating bulb iscombined with a closure cap for a container and wherein the bulb and capare adjustable so that they can be at times shifted to a positionallowing the pipet to reach a bottom corner portion of the associatedcontainer, whereby by tilting the container practically all the liquidin the container may be ultimately removed, thus minimizing waste of theliquid.

A still further object of the invention is to provide an improvedbulb-operated pipet which cuts off filling pressure when its mainchamber is filled and reduces the possibility of drawing liquid into itsoperating bulb, the time period required for filling the main chamberbeing a definite value so that the operator can terminate the fillingpressure at the end of such time period, making it unnecessary for himto closely watch the chamber during the filling operation, the pipetbeing thereby usable with high speed and precision while requiring aminimum amount of visual and mechanical effort and requiring arelatively low degree of dexterity on the part of the operator.

Further objects and advantages of the invention will become apparentfrom the following description and claims, and from the accompanyingdrawings, wherein:

FIG. I is a vertical cross-sectional view taken through a typicalbulboperated liquid transfer pipet constructed in accordance with thepresent invention.

FIG. 2 is a vertical cross-sectional view of a modified form of pipet inaccordance with the present invention,

shown combined with a screw cap closure on a liquid container.

FIG. 3 is a vertical cross-sectional view of the pipet of FIG. 2, shownwith its operating bulb and screw cap in an extended position enablingthe pipet to reach residual liquid in a bottom corner portion of theassociated container, with the container tilted.

FIG. 4 is a vertical cross-sectional view of the pipet of FIG. 2, showncombined with the ground glass closure stopper of a reagent bottle.

FIG. 5 is a vertical cross-sectional view of the pipet of FIG. 2, showncombined with the rubber stopper of a laboratory vial.

FIG. 6 is a fragmentary vertical cross-sectional view showing a furthermodification of a bulb-operated liquid transfer pipet according to thepresent invention.

Referring to the drawings, and more particularly to FIG. 1, 11 generallydesignates a typical liquid transfer pipet according to the presentinvention. The pipet comprises a tubular main barrel 12 having a reducedbottom inlet conduit portion 13 integrally connected to the main barrel12 by a tapered portion 14. Main barrel 12 is provided with a reducedtop stem 15 of substantial length having a capillary bore 16 which maybe from about 0.002 to 0.02 inch in inside diameter. Slidably andsealingly mounted on stem 16 is a filling bulb 17 of resilientdeformable material, such as rubber or the like. Bulb l7-is providedwith a top vent aperture 18 adapted to be at times sealingly covered bythe users finger, for example, after the bulb has been squeezed to acollapsed condition and it is desired to draw liquid into barrel [2, orwhen it is desired to expel liquid from the barrel after it has beenfilled.

The barrel 12 has a generally frusto-conical top wall 19, with the stem15 integrally formed at its apex. When liquid drawn into the barrel 12reaches top wall 19, it is thereafter forced into the capillary bore 16,which imposes a high resistance to flow and thereby substantiallyabruptly terminates intake of liquid into the barrel. With a givenpipet, the filling time will therefore be substantially constant, and anoperator can quickly learn to remove his finger from the aperture 18 atthe end of the filling time period after a few experimental usages ofthe pipet. Alternatively, the operator can easily visually determinewhen the liquid reaches top wall 19. In either case, the intake flow isso retarded by the action of the capillary bore 16 that the operator hassufficient time to remove his finger from aperture 18 after barrel I2 isfilled to prevent liquid from being forced completely through and beyondthe capillary bore 16.

After filling, the surface tension of the liquid in the capillary bore16 acts in a manner to cause this liquid to seal the bore and to therebyallow the pipet to be transported without loss of liquid from the filledbarrel 12. The liquid can be thereafter discharged from the pipet bysealing vent aperture 18 with the users finger and applying squeezingpressure to the bulb 17.

In the event that during filling the operator fails to release hisfinger from the vent aperture 18 in time to prevent liquid fromoverflowing from the top end of capillary bore 16 into the bulb 17, itwill not re-enter the bore when the pipet is discharged in theabovedescribed normal manner since it will tend to accumulate at thebottom of the bulb around the stem 15. The possibility of such overflowcan be minimized by making stem 15 of substantial length, for example,from about 3/4 inch to as much as 2-1/2 inches. To further reduce thepossibility of re-entry of overflow liquid from bulb 17 into thecapillary bore when liquid is discharged from the pipet, the top end ofthe capillary stem portion may be made conical, as shown at 21 in FlGS.2 to 5, or frusto-conical, as shown at 22 in FIG. 6.

As shown in FIG. 6, the capillary bore 16 may be formed merely in asolid top extension 20 of the pipet main barrel, wherein no reduction indiameter of the top portion of the main barrel body is necessary.

Although the capillary bore 16 is of substantial length, its insidediameter is so small that its entire volume, compared to the measuredvolume in the main barrel of the pipet, is not large enough to cause anysignificant error in the measured volume of liquid dispensed by thepipet.

Referring now to FIGS. 2 and 3, a pipet 23 generally similar to thepreviously described pipet 11 is shown combined with a screw cap closure24 threadedly engageable on the neck 25 of a conventional bottle 26. Inthis embodiment the operating bulb, shown at 27, is integrally formedwith a generally frusto-conical annular bottom sealing stopper 28 whichis received beneath an inturned annular top lip or flange 29 of thegenerally ring-shaped rigid screw cap 24, so that when the cap 24 istightened the stopper element is clamped sealingly on the top rim of thebottle neck 25. The top stern, shown at is slidably and sealinglyengaged through the thickened bottom portion 30 of the bulb 27concentrically with stopper 28. With the screw cap 24 loosenedsufficiently to allow atmospheric air to enter the bottle through theneck 25, the pipet assembly can be employed in the same manner aspreviously described to dispense accurately measured liquid volumes fromthe bottle 26. To remove practically all of the liquid from the bottle,so as to minimize waste, the cap 24 may be unscrewed from the neck ofthe bottle and the bulb 27 can be adjusted upwardly on the stem 15', asshown in FIG. 3, whereby the inlet conduit portion 13 can be maneuveredto reach the lowermost corner portion of the bottle, in the tiltedposition of the bottle illustrated, whereby to draw the last remainingamounts of liquid into the pipet.

In the embodiment illustrated in FIG. 4, the pipet assembly of HG. 2 iscombined with a stopper plug 31 similar to the ground glass sealing plugof a reagent bottle 32. The stopper plug 31 is of hollow constructionand has a top wall which is centrally apertured to receive a rubber, orsimilar resilient deformable grommet 33, and the stern portion 15' ofthe pipet assembly is slidably and loosely engaged through said grommetand the pipet assembly may be employed in the same manner as describedabove in connection with FIGS. 2 and 3 to dispense accurately measuredvolumes of liquid reagent from the bottle 32.

In the embodiment illustrated in FIG. 5, the pipet assembly of FIG. 2 isemployed with a centrally apertured rubber or similar stopper plug'34similar to the stopper plug of a conventional serum via] 35. The barrel12 of the pipet assembly is loosely engaged through the central apertureof the plug 34, and the pipet assembly may be employed in the samemanner as described above in connection with FlGS. l, 2 and 4.

In each of the embodiments illustrated in the drawings and describedabove, the capillary bore at the top end of the pipet barrel serves tol) inhibit further entry of liquid into the barrel when the measuringcavity therein has been completely filled, and thereby give the operatortime to remove his finger from the vent aperture l8, and 2) provide aretention means, namely, the capillary column of liquid in the bore, toenable the filled pipet to be safely transported without risk of loss ofits contents, since the capillary column provides a holding effectsufficient to support the liquid in the filled pipet barrel. ln pipetsof the type previously employed, either of the mouth-operated orbulb-operated type, the operator must place and hold his finger insealing engagement with the top end of the pipet or other vent apertureof the pipet when the pipet is to be transported, calling forconsiderable dexterity on the part of the operator. This is notnecessary with the above-described apparatus.

In operating any of the above-described forms of the present invention,the operating bulb is first squeezed to a collapsed condition, afterwhich, with the intake end of the pipet immersed in the liquid to bedispensed, the operator covers aperture 18 with his finger and allowsthe bulb to resume its normal shape. This draws liquid into the pipetbarrel, filling the pipet barrel cavity, the liquid rising therein untilit enters the capillary bore 15, at which time the filling action isabruptly terminated by the resistance imposed by the capillary bore, asabove described. The operator then removes his finger from aperture 18and the pipet can then be transported to the intended receiving vesselor receptacle, into which the liquid in the pipet may be then dischargedby again covering the aperture 18 and squeezing the operating bulb.

In the various different forms of the invention abovedescribed theportion of the barrel carrying the operating bulb is preferably ofcylindrical shape and of uniform cross-sectional diameter, whereby tofacilitate adjustment of the bulb therealong as required.

While certain specific embodiments of liquid transfer pipets have beendisclosed in the foregoing description it will be understood thatvarious modifications within the spirit of the invention may occur tothose skilled in the art. Therefore it is intended that no limitationsbe placed on the invention except as defined by the scope of theappended claims.

What is claimed is:

l. A liquid transfer pipet comprising a barrel member having aliquid-receiving cavity portion and an intake conduit element at one endof said barrell member communicating with said cavity portion, theopposite portion of said barrel member being formed with a capillarybore coextensive in length therewith in communication with said cavityportion and opening at the opposite end of the barrel member, and aflexible operating bulb sealingly engaged on and slidably receiving saidopposite portion, said bulb being formed with an upper vent openingadapted to be sealingly engaged at times by an operator, and whereinsaid opposite portion of the barrel member is of substantial length andof uniform cross-sectional size and shape and is much smaller than thebulb, whereby the bulb may be adjusted to a position along said oppositeportion wherein said opposite portion projects upwardly a substantialdistance through an opening in the bulb to define within said bulb abovesaid opposite portion an air space and within said bulb below saidopposite portion an overflow space of substantial volume in the bottomof the bulb around said opposite portion, and said upper vent openingbeing in communication with said air space, and whereby liquidaccumulating in said overflow space will not re-enter said capillarybore when the bulb is squeezed to discharge liquid from the pipet.

2. The liquid transfer pipet of claim 1, and wherein said capillary borehas an inside diameter of between 0.002 and 0.02 inch.

3. The liquid transfer pipet of claim I, and wherein the end of saidopposite portion received in the operating bulb is tapered, whereby tominimize the possibility of re-entry of overflow liquid from the bulbinto the capillary bore when liquid is discharged from the pipet.

4. The liquid transfer pipet of claim 1, and wherein of circularcrosssectional shape.

1. A liquid transfer pipet comprising a barrel member having aliquid-receiving cavity portion and an intake conduit element at one endof said barrell member communicating with said cavity portion, theopposite portion of said barrel member being formed with a capillarybore coextensive in length therewith in communication with said cavityportion and opening at the opposite end of the barrel member, and aflexible operating bulb sealingly engaged on and slidably receiving saidopposite portion, said bulb being formed with an upper vent openingadapted to be sealingly engaged at times by an operator, and whereinsaid opposite portion of the barrel member is of substantial length andof uniform cross-sectional size and shape and is much smaller than thebulb, whereby the bulb may be adjusted to a position along said oppositeportion wherein said opposite portion projects upwardly a substantialdistance through an opening in the bulb to define within said bulb abovesaid opposite portion an air space and within said bulb below saidopposite portion an overflow space of substantial volume in the bottomof the bulb around said opposite portion, and said upper vent openingbeing in communication with said air space, and whereby liquidaccumulating in said overflow space will not reenter said capillary borewhen the bulb is squeezed to discharge liquid from the pipet.
 2. Theliquid transfer pipet of claim 1, and wherein said capillary bore has aninside diameter of between 0.002 and 0.02 inch.
 3. The liquid transferpipet of claim 1, and wherein the end of said opposite portion receivedin the operating bulb is tapered, whereby to minimize the possibility ofre-entry of overflow liquid from the bulb into the capillary bore whenliquid is discharged from the pipet.
 4. The liquid transfer pipet ofclaim 1, and wherein said opposite portion is in the form of a reducedstem of substantially uniform cross-secTional size, whereby theoperating bulb may be at times adjusted in position along said reducedstem.
 5. The liquid transfer pipet of claim 1, and wherein the capillarybore is sufficiently small in inside diameter and of sufficient lengthto develop the capillary sealing action required to support the totalvolume of liquid receivable in said cavity.
 6. The liquid transfer pipetof claim 1, and wherein said opposite portion is in the form of areduced stem of circular crosssectional shape.